Transcript Dental cement

Dental cement
Topic
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General requirements for dental
cements
Classification of dental cements
Component and properties
Setting reaction
Mixing process
The uses of dental cements
Definition
Dental cements : materials made from two
components, powder and liquid, mixed
together.
Powder + Liquid
Pastelike or flowable material
Hardens to a rigid solid
Uses of dental cements
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Luting agent
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Temporary cement
Permanent cement
Pulp protection or cavity sealer
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Cavity varnish
Liner
Base
Uses of dental cement
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Filling
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Temporary filling
Permanent filling
Others
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Root canal sealer
Calciumhydroxide cement
Bite registration material
Luting agent
Luting : the use of moldable substance to
seal a space between two component.
Most dental treatment necessitate
attachment of prostheses to the teeth
by means of luting agent.
General requirements for
luting agents
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Biocompatibility
Retention
High tensile strength, fracture
toughness, fatique strength
Good marginal seal
General requirements for
luting agents
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Low film thickness
Ease of use
Radiopacity
Aesthetics
Film thickness
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The thickness of film between two flat
surface
The maximum allowable thickness is 25
µm (ADA specification No. 96)
Low film thickness value is preferred
Cement base
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A thick layer of cement (>0.75mm) is
applied under restoration to protect
pulp against injuries.
The base should be strong enough to
resist the condensation force during the
placement of restoration.
Well insulation ability
Good sealing
Classification of dental
cements
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Conventional cement
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Zinc phosphate cement
Zinc oxide-eugenol cement
Polycarboxylate cement
Glass ionomer cement
Resin-base cement
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Resin cement
Resin modified glass ionomer cement
Conventional cement
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Typically powder/liquid system
Liquid is an acid
Powder is a base ; insoluble in oral fluid
When mixed together  Acid-base
reaction
Zinc Phosphate cement
Zinc phosphate cement
Powder
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Zinc oxide
Magnesium
oxide
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Liquid
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Phosphoric acid
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Water
Alumenium
phosphate
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ZnO
ZnO
Zn+
ZnO
Zn+
Zinc
aluminophosphate
gel
Unreacted
ZnO
Unreacted
ZnO
Unreacted
ZnO
Zinc aluminophosphate matrix
Unreacted
ZnO
Setting reaction
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Exothermic reaction
Adding of water can accerlate the
reaction.
Loss of water can lengthen the setting
reaction.
Working time and setting time
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Working time commonly is 3-6 minute
Setting time is 2.5-8 minute(ADA
specification No.96)
Depending on the manufacturer instruction
How to extend the setting
time ?
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Reducing powder/ liquid ratio
recommended}
{not
Mixing on the cool glass slap {no moisture}
Mixing over a large area.
Mixing cements in increments.
Mixing procedure
There are three steps:
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First : add the small amount of powder
into the liquid
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To achieve the slow neutralization of the
liquid.
To control the reaction.
Mixing procedure
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Second : Larger amount of powder is
added to liquid
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For further saturation of liquid to newly form
zinc phosphate.
This steps may not effect by heat released from
the reaction.
{because of the less amount of unreacted acid}
Mixing procedure
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Finally: the small amount of powder is
added again
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To control the optimum consistency
4
2
1
5
3
7
8
6
4
2
1
5
3
7
8
6
Characteristic properties
Setting time at 37O
5 – 9 minutes
Minimum compressive
strength
75 MPa
Maximum film
thickness
Maximum Solubility
25 µm (for luting the
prostheses)
0.2% by weight
ADA specification NO.8 for Zinc phosphate cement
Effects of manipulation on
some properties.
Manipulative
variables
Decreased
powder/liquid ratio
Increase rate of
powder incorporation
Increase mixing
temperature
Water contamination
Properties
Copressive Film
strength
thickness
Solubility
Initial
acidity
Setting
time
Biocompatibility
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Acid can penetrate into the dentinal
tubule  irritate pulp
pH of cement
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Liquid = 2.0
3 minutes after mixing = 4.2
1 hour = 6
48 hours = 7
Modified zinc phosphate
cement
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Fluoride cement
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Add Stannous fluoride
Higher solubility/ Lower strength
Zinc silicophosphate
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Zinc phosphate + Silicate
Higher strength/ lower solubility
Fluoride released
Translucency
Clinical applications
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Zinc phosphate cement
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Luting agent
Base and temporary filling
Modified zinc phosphate
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Luting prostheses
Luting the orthodontics band
Zinc oxide-eugenol cements
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Lower strength than Zinc phosphate
cement.
Sedative effect
Usually used as temporary filling
Zinc oxide-eugenol cement
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Simple ZOE
Reinforced ZOE
EBA cement
Compositions of simple ZOE
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Powder
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Zinc oxide
Rosin : reduce the brittleness of the set
cement
Zinc stearate : plastcizer
Zinc acetate : improve strength
Liquid
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Eugenol and olive oil
Setting reaction
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First
ZnO + Eugenol --
water
Zn(OH)2
Second
Zn(OH)2+2HE  ZnE2+H2O
Setting reaction
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Water accelerates the reaction
Zinc eugenolate is easily hydrolized by
moisture
Manipulation
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Paste/paste
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Mix two equal pastes together until it
obtains the homogeneous color.
Powder/liquid
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Usually 4/1 for maximum strength
Mix the large increment, firstly
Not require cool glass slap
Classification
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Type I
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Type II
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Permanent cementation
Type III
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Temporary luting cement
Temporary restoration [for a few days]
Type IV
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Cavity liner
Specification requirements
Type
Setting Compressive Solubility Film
time
strength
thickness
[%]
[min]
[MPa]
[µm]
Type I
4-10
35 maximum
2.5
25
Type II
4-10
35 maximum
1.5
25
Type III 4-10
35 maximum
1.5
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Reinforced ZOE
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Used as the intermediate restorative
materials (IRMTM)
Add 10-40% resin polymer in the
powder for strengthening the set
cement
Compressive strength 35-55 MPa
EBA cement
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Powder
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Liquid
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Add 20-30% of aluminium oxide
Add 50-60% ethoxybenzoic acid in eugenol
Compressive strength 55-75 MPa
Clinical applications
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Base
Temporary cementation
Permanent cementation
If cement contains eugenol, it is not to use with
resin restorative material.
Zinc polycarboxylate cement
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Or called Zinc polyacrylate cement
The first adhesive cement
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More biocompatibility than zinc
phosphate cement
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Bond to tooth structure and metal
Polyacrylic acid have more molecular weigth
Moderate strength/ moderate solubility
Composition
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Powder [the same as zinc phosphate
cement ]
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Zinc oxide
Magnesium oxide
Stannous fluoride
Liquid
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Aqueous solution of polyacrylic acid
Other carboxylic acid
Manipulation
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Mix first half of powder to liquid to
obtain the maximum length of working
time.
The reaction is thixotropic
The viscosity decreases when the shear rate
increases
Setting reaction
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Like zinc phosphate cement
Retarded by cool environment
Bonding to tooth structure
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The polyacrylic acid is believed to react
with calcium ion via the carboxyl group.
The adhesion depends on the unreacted
carboxyl group.
Specification requirements
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Setting time at 37OC: 9 minutes
Maximum film thickness: 25µm
Minimum compressive strength: 50 MPa
Maximum solubility: 0.2%
Applications
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Cement inlays or crowns
Used as base
Temporary filling
Lute the stainless steel crown
Glass ionomer cement
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Or called Polyalkynoate cements
Conventional glass ionomercement
Resin-modified glass ionomer cement
[RMGICs]
Powder + Liquid/ Powder + water/
Encapsulated
Composition
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Powder
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Calcium aluminum fluorosilicate glass
Liquid
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Polyacid
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Copolymer of polyacrylic / itaconic acid
Copolymer of polyacrylic / maleic acid
Add tartaric: accelerator
Setting reaction
There are three stages:
 Dissolution
 Gelation
 Hardening.
Water hardening or water setting
Polyacid liquid
Hydrogen
ions
Ca2+
Al3+
Glass core
FSilica gel
Polyacid liquid
Ca2+
Al3+
F-
-COOH
Cross-linked
polyacid
Gelation
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Calcium ions have more reactivity than
aluminium ions.
This is critical phase of contamination.
Polyacid liquid
Al3+
-COOH
Cross-linked
polyacid
Hardening
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Last as long as 7 days.
The reaction of aluminium ions provides
the final strength of set cement.
Glass
core
Cross-linked polyacid
Silica gel
Properties
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Film thickness is similar or less than
zinc phosphate cement.
Setting time 6 to 8 minutes from start
of mixing.
Less pulpal irritation.
Bacteriocidal or bacteriostatic.
Prevent caries.
Strength
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The 24-hour compressive strength is
greater than zinc phosphate cement.
The compressive strength increase to
280MPa between 24 hours to 1 year
after initial setting.
Bonding
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It can be chemically bonded to the
tooth structure.
The mechanism of bonding is the same
as polyacrylate cement.
The dentine bond strength may be
lower than polyacrylate because of
technique sensitivity.
Modified GI
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Cermet
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Combination of glass and metal
No significantly improve the strength
More wear resistance and short setting
time
Resin-modified GI
Resin-modified glass ionomer
cement
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Add polymerizable function groups
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Both chemical & light curing
Overcome moisture sensitive & low early
strength
Names: Ligth cured GICs, Dual-cured GICs,
Tri-cured GICs, Hybrid ionomer,
Compomers, Resin-ionomers
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Setting reaction
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Polymerization
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Acid-base reaction
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initial setting
maturing process & final strength
Heat released from the polymerization
reaction.
Properties
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Higher strength than conventional GI
Higher adhesion to resin material
Less water sensitivity
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Can be polished after curing
Relative properties of a glass ionomer and
a resin-modified GI cements
Property
GIC
RMGIC
Working time
2 min
3 min 45 sec
Setting time
4 min
20 sec
Compressive
strength
202 MPa
242 Mpa
Tensile strength
16 Mpa
37 Mpa
Applications
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Type I : Luting agent
Type II : Filling material
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Type III : Base and liner
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Conventional GI for cementation
GI filling material
Adhesive resin cement
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Occur later from the direct filling resin
Become popular because of the
improved properties, high bond
strength.
Resin cement is flowable composite
resin.
Composite resin cement
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Composite :
Resin matrix + inorganic filler
Silane
coated
Composition
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Filler
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Silica
Matrix
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Bis-GMA (polymer)
The fillers binds with matrix by
silane coupling agent
Setting reaction
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Polymerization
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Chemical activation
Light activation
Dual activation [chemical and light]
Preparations
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Powder / liquid
Chemical, light, or dual cure
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2 paste system [base / catalyst]
Chemical, light, or dual cure
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Single paste
Light cure
Bonding system
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Bond with the tooth surface by enamel
an dentine bonding system.
Bond with metal by using metal primer.
Bond with ceramic restoration by
treating the surface of porcelain with
silane coupling agent
Properties
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Very good bond strength
High compressive strength
Water sensitive
Might irritate pulpal tissues
Applications
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Tooth color filling materials
Luting cements
Calcium hydroxide cement
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Used as base and
liner
High pH value
Good
biocompatibility
Composition
2 Pastes system
 Base
Salicylate  reaction
 Calcium tungstate and barium sulfate
 radiopacity
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Catalyst
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Calcium hydroxide
Properties
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Lower compressive strength than others
Resist to the condensation force of
amalgam filling
High pH 9.2-11.7 [Alkaline]
Bactericidal
High solubility
Properties
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Stimulate the secondary dentine
formation in the area of thin dentine
[<0.5mm]
Stimulate the dentine formation in the
exposed-pulp lesion [Direct pulp
capping]
Comparable properties of
cements
Compressive strength [MPa]
160
140
120
100
80
60
40
20
0
Zinc phosphate
Polycarboxylate
Zhen Chun Li and Shane N. White, 1999
GIC
RMGIC
Resin cement
Bond strength
Separation forces [MPa]
300
250
200
150
100
50
0
Zinc phosphate
GIC
Sule Ergin and Deniz Gemalmaz, 2002
RMGIC
Resin
Film thickness [µm]
50
40
30
20
10
0
Zinc phosphate
Polycarboxylate
Shane N. White, Zhaokun Yu, 1992
GIC
RMGIC
Resin
Others
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Solubility
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ZOE > Polycarboxylate > Zinc
phosphate~GIC > Resin cement
Irritation to pulp tissues
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Resin~Zinc phosphate > GIC >
Polycarboxylate > ZOE~Calcium hydroxide
References
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Textbooks
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Kenneth J. Anusavice
Phillips’ science of dental materials
11th edition
W.B. Saunders company 2003
References
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Textbook
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Robert G. Craig
Restorative dental materials
9th edition
Mosby company 1993
References
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Textbook
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Richard van Noort
Introduction to dental materials
2nd edition
Mosby company 2002
References
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Journals
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Li ZC, White SN. Mechanical properties of dental
luting cements. J Prosthet Dent 1999;81(5):597609
White SN, Yu Z. Film thickness of new adhesive
luting agents. J Prosthet Dent 1992;67(6):782-90
Ergin S, Gemalmaz D. Retentive properties of five
luting cements on base and noble metal copings. J
Prosthet Dent 2002;885:491-97